The peer communication (libconn or pconn) library provides the TCP client and server interface for daemons and applications running on the Routing Engine, and for MultiServices PICs running a JUNOS kernel.
This library is the recommended form of TCP client-server communication because libconn is designed to work optimally with the JUNOS architecture. For example, if you did not use libconn, a switchover to the backup Routing Engine would terminate the connection; libconn handles this transparently and preserves the connection.
Communication can be Routing Engine to Routing Engine, Routing Engine to MultiServices PIC, or MultiServices PIC to MultiServices PIC.
For an introduction to this library, see The Peer Communication API and Using the libconn API For Inter-Module Communications.